I'm currently in college doing a BTEC Extended Diploma in Level 3 Health and Social Care and I'm going to bre doing my year 2 in September as well as applying for University. I was wondering if I am able to study Criminology with maybe another subject such as Psychology or Sociology in University with my Btec course

Yes you will be able to but look on the UCAS site at all the criminology courses and the variations or specialisms they allow. Go to the best uni you can. There were a few helath and social care plus criminology courses, one at Sunderland and another at Wolverhampton, but try and go to the best uni .